Tropical Storm Iselle is lashing the Big Island of Hawaii with winds close to hurricane force, high waves up to 25 feet in height as well as heavy rain. It is predicted to move across the Big Island, interacting with the nearly 14,000 foot tall peaks of Mauna Kea and Mauna Loa, and emerging south of Oahu later on Friday local time.

The storm made landfall at 2:30 a.m. HST, about five miles east of Pahala. Although the storm's winds had weakened below hurricane strength, to 60 miles per hour with higher gusts, Iselle still poses a threat to Hawaii's Big Island for several reasons.

Iselle is the first tropical storm to make landfall on the main Hawaiian Islands in 22 years, since 1992's devastating Hurricane Iniki hit Kauai. The storm is unique for approaching Hawaii from the east, where cool ocean waters and strong upper atmospheric winds typically overcome such storms and deflect them before they reach the island state. It is just the second tropical storm ever to hit the Big Island, and is the strongest to do so.

Hawaiians are not accustomed to these storms, and the 14,000-foot mountains on the Big Island will create unique hazards, making winds and rainfall totals vary considerably across the island, with some areas likely to receive well over a foot of rain.

Hot on the heels of Iselle is Hurricane Julio, which may affect Hawaii over the weekend.

Iselle mainly a heavy rain threat now

3:11 p.m. ET:While some parts of the Hawaiian Islands continue to experience winds of 50 miles per hour or greater, satellite data and surface observations indicate that the storm itself has weakened considerably since it came ashore on the Big Island at about 2:30 a.m. HST. The storm is now a heavy rain threat, with more than a foot of rain already being reported in the southeastern part of the Big Island. Heavy, gusty rain showers are affecting the other islands, where localized flash flooding is also possible.

As Tropical Storm Iselle continues to weaken while affecting Hawaii, another storm — Hurricane Julio — lurks about 800 miles to the east, moving generally in the direction of the island state. The storm has weakened from its peak intensity, when it had sustained winds of 120 miles per hour, and it is predicted to pass just to the north of the Hawaiian islands over the weekend as a Category One hurricane. Its impacts on the state are uncertain at this time, but just the prospect of two intense tropical cyclones hitting Hawaii in a span of 10 days or less is unprecedented.

Meanwhile Hurricane Julio waits in the wings

12:10 p.m. ET: As Tropical Storm Iselle continues to affect Hawaii, another storm — Hurricane Julio — lurks about 800 miles to the east, moving generally in the direction of the island state. The storm has weakened from its peak intensity, when it had sustained winds of 120 miles per hour, and it is predicted to pass just to the north of the Hawaiian islands over the weekend as a Category One hurricane. Its impacts on the state are uncertain at this time, but just the prospect of two intense tropical cyclones hitting Hawaii in a span of 10 days or less is unprecedented.

Mountains take their toll

11:20 a.m. ET: Tropical Storm Iselle appears to be weakening quite quickly, due in part to its interaction with the peaks of Mauna Kea and Mauna Loa, which both rise to a height of nearly 14,000 feet. These mountains are serving to disrupt the storm's low-level circulation, and may have deflected the storm center to the south shore of the Big Island, based on radar images, thereby keeping the strongest winds away from Hilo, the most populated city on the island.

Impacts: Waves

11:15 a.m. ET: High waves have been battering the east and southeast facing shoreline of the Big Island, with wave heights up to at least 25 feet in places. Because Hawaii does not have a shallow continental shelf extending for miles off the coast, storms don't cause surges of water as they do in other places. Instead, high waves are what can cause damage in Hawaii, since the ocean floor drops off quickly right off the beaches.

High waves are likely to affect the rest of the Hawaiian islands on Friday, even though tropical storm force winds may not be felt everywhere. Waves of 10 to 15 feet, combined with high tide, could cause coastal flooding along east and southeast facing shorelines in Maui, Oahu, and Kauai, according to the National Weather Service.

Impacts: Wind

10:00 a.m. ET: According to the latest information from the National Weather Service in Honolulu, Hawaii, wind gusts will be strongest "over mountainous terrain, through passes, and where winds blow downslope." The NWS is also warning that the winds affecting the upper floors of high rise buildings will be much stronger than those at ground level. will be significantly stronger than those near ground level.

Power outages on the Big Island are around 21,800 now with most outages in Lower Puna, North Kohala, Hilo & along Hamakua Coastline. #Iselle

Because of the strong winds, Hilo International Airport is closed, having already recorded maximum wind gusts of 44 miles per hour. There have been reports of wind damage to homes to the southeast of Hilo, according to The Weather Channel.

Update: Hurricane Warning for the Big Island has been discontinued. It is now being replaced by a Tropical Storm Warning. #Iselle#hiwx

Impacts: Rainfall

10:40 a.m. ET: Heavy rains are piling up in the Big Island, with reports of at least eight inches having already fallen. As the winds blow up the steep slopes of Mauna Kea and Mauna Loa mountains, the air will cool and condense, leading to even heavier rainfall there. So far, the heaviest rainfall has wobbled with the storm center to the south of Hilo, due to the storm's interaction with the mountains.

Flash flood watches and warnings have been posted for all of the main Hawaiian islands on Friday.

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